This invention relates in general to electronic controllers for controlling a plurality of output devices. In particular, this invention relates to a method for operating an electronic controller in a manner which efficiently generates output signals to a relatively large number of output devices, yet which utilizes only a relatively small amount of programming code to accomplish this.
Many industrial, commercial, and agricultural vehicles in use today are provided with one or more output or accessory devices to assist an operator of the vehicle in performing various functions, such as lifting, loading, or moving articles. For example, a typical refuse truck includes a plurality of hydraulic actuators which are connected to arms and other devices for lifting and emptying refuse receptacles and packing refuse within a container. Also, many construction vehicles, such as excavators and bulldozers, include a plurality of hydraulic actuators which are connected to shovels, buckets, and lifting arms. In the past, these various accessory devices have been manually operated by the operator of the vehicle by means of a hydraulic control system. A conventional hydraulic control system includes a source of pressurized fluid which is connected through a plurality of control valves to the various hydraulic actuators. By manually opening and closing the control valves, the operator can control the operations of the hydraulic actuators, as well as the accessory devices connected thereto, in a desired manner.
More recently, because of significant advances in electronic controller technology, many industrial, commercial, and agricultural vehicles are provided with an electronic control system for automatically performing some or all of the operations which have previously been performed manually. A typical electronic control system includes one or more electronic controllers for automatically controlling the operation of the control valves and, therefore, the various accessory devices. In a typical automated hydraulic control system, the electronic controller is responsive to one or more input signals for generating output signals to electrically operated solenoids which control the operation of the control valves. The electronic controller may, for example, control the timing and quantity of pressurized fluid supplied from the source to the hydraulic actuators so as to control the movement of the accessory devices in a desired manner. Thus, the electronic controller relieves the operator of the vehicle from many of the control operations which were previously performed manually.
Because of cost and physical constraints, the electronic controller typically provided within a vehicle for controlling the various accessory devices is embodied as a microprocessor. Generally speaking, a microprocessor is a general purpose digital computer which is relatively small in size, memory space, and computational capacity. As a result, the ability of such a microprocessors to control the operation of a plurality of accessory devices is somewhat limited. In view of this, it is important to program and operate these microprocessors in such a manner as to maximize the efficiency thereof. Thus, it would be desirable to provide a method for operating an electronic controller in a manner which efficiently generates output signals to a relatively large number of output devices, yet which utilizes only a relatively small amount of programming code to accomplish this.